This application relates to U.S. application Ser. No. 08/130,580, "Wobble Correction by Dual Spot Pixel Intensity Proportioning" (Common Assignee) Filed concurrently herewith.
This invention relates to a sensor for a raster scanning system, and more particularly, to a raster scanning system which utilizes two elements to detect the position of a scanning light beam relative to a reference level and also detect the start of the scan position.
Referring to FIG. 1, a conventional raster scanning system utilizes a light source 12, a collimator 14, a pre-polygon optics 16, a multi-faceted rotating polygon mirror 18 as the scanning element, a post polygon optics 20 and a photosensitive medium 22. The light source 12, which can be a laser source, produces a light beam 24 and sends it to the polygon 18 through the collimator 14 and the pre-polygon optics 16. The rotating polygon has a plurality of facets 26, each of which is a plane mirror. The facets 26 of the rotating polygon mirror 18 reflect the light beam 24 and also cause the reflected light 24 to revolve about an axis near the center of rotation of the rotating polygon mirror 18 scanning a line. This reflected light beam can be utilized to scan a document at the input end of an imaging system as a raster input scanner or can be used to impinge upon a photographic film or a photosensitive medium 22, such as a xerographic drum at the output of the imaging system.